RESUMO
Four rapid methods for detection of Salmonella, (i) the conventional fluorescent-antibody (FA) technique, (ii) a rapid direct FA technique, (iii) microcolony FA, and (iv) enrichment serology (ES), were compared with conventional cultural procedures. A total of 347 subsamples representing 16 different food prototypes, alleged to be naturally contaminated with Salmonella, were analyzed. From these samples, 52 were found to contain Salmonella by cultural methods. Conventional FA identified all 52 culturally positive samples, ES identified 51, microcolony FA identified 48, and the rapid FA method identified 34. The number of false-positive samples for each procedure was: ES-selenite, 7; tetrathionate, 8; rapid FA, 26; microcolony FA, 33; conventional FA-selenite, 27; tetrathionate, 26. Tetrathionate enrichment was found to be superior to selenite for Salmonella recovery from most foods, but the concurrent use of both media allowed maximum recovery.
Assuntos
Técnicas Bacteriológicas , Imunofluorescência , Microbiologia de Alimentos , Salmonella/isolamento & purificação , Meios de Cultura , Estudos de Avaliação como Assunto , Reações Falso-Negativas , Reações Falso-Positivas , Contaminação de Alimentos , Métodos , Salmonella/crescimento & desenvolvimento , Selênio , TiossulfatosRESUMO
The effects of temperature and length of incubation on ochratoxin A production in various substrates were studied. The optimal temperature for toxin production by Aspergillus ochraceus NRRL-3174 was found to be around 28 C. Very low levels of ochratoxin A are produced in corn, rice, and wheat bran at 4 C. The optimal time for ochratoxin A production depends on the substrate, ranging from 7 to 14 days at 28 C. Ochratoxin B and dihydroisocoumaric acid, i.e., one of the hydrolysis products of ochratoxin A, were produced in rice but at levels considerably lower than ochratoxin A. No ochratoxin C was produced in rice at 28 C. When added to rice cereal or oatmeal, the toxin was found to be very stable over prolonged storage and even to autoclaving for 3 hr.
Assuntos
Aspergillus/metabolismo , Cumarínicos/biossíntese , Grão Comestível , Contaminação de Alimentos , Microbiologia de Alimentos , Micotoxinas/biossíntese , Cromatografia em Camada Fina , Manipulação de Alimentos , Ocratoxinas/análise , Ocratoxinas/biossíntese , Oryza , Esterilização , Temperatura , Fatores de Tempo , Triticum , Zea maysRESUMO
Samples of freshly harvested and remoistened corn, of various moisture contents, were stored at different temperatures; analyses for aflatoxin content were made periodically. At moisture levels above 17.5% and at temperatures of 24 C or warmer, aflatoxins were formed by Aspergillus flavus present in the original epiphytic mycoflora. Remoistened dried corn was subject to more rapid fungal deterioration and aflatoxin formation than freshly harvested corn. Screening of the fungi present in the corn revealed aflatoxin production only by A. flavus. The toxigenic strains produced only aflatoxins B(1) and B(2).
